Many modern sunscreens are formulated to achieve high sun protection factors (SPF). It is desirable that such sunscreens be able to remain on the skin for long periods of time, even during or after immersion in water, or in the presence of perspiration. The ability of a sunscreen to remain on the skin is referred to herein as its substantivity.
For convenience of manufacture, and to achieve desirable cosmetic properties such as ease of spreading, most sunscreen compositions are formulated as emulsions comprising an oil phase and a water phase. A disadvantage of emulsions is that they may involve the use of hydrophilic surfactants, and these can significantly reduce the substantivity of the associated sunscreen.
It is an object of at least one form of the present invention to provide a sunscreen composition that has substantial substantivity.